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What birds can teach us about animal intelligence
February 10, 2015
By Leyre Castro
and Ed Wasserman
People are fascinated by the intelligence of animals. In fact, cave paintings
dating back some 40,000 years suggest that we have long harbored keen interest
in animal behavior and cognition. Part of that interest may have been practical:
animals can be dangerous, they can be sources of food and clothing, and they can
serve as sentries or mousers.
But, another part of that fascination is purely theoretical. Because animals
resemble us in form, perhaps they also resemble us in thought. For many
philosophers--including René Descartes and John Locke--granting intelligence to
animals was a bridge too far. They especially deemed abstract reasoning to be
uniquely human and to perfectly distinguish people from "brutes." Why? Because
animals do not speak, they must have no thoughts.
Nevertheless, undeterred by such pessimistic pronouncements, informed by
Darwin's theory of evolution, and guided by the maxim that "actions speak more
loudly than words," researchers today are fashioning powerful behavioral tests
that provide nonverbal ways for animals to disclose their intelligence to us.
Although animals may not use words, their behavior may serve as a suitable
substitute; its study may allow us to jettison the stale convention that thought
without language is impossible.
A recent research collaboration between Moscow State University and here at the
University of Iowa has discovered that crows exhibit strong behavioral signs of
analogical reasoning--the ability to solve puzzles like "bird is to air as fish
is to what?" Analogical reasoning is considered to be the pinnacle of cognition
and it only develops in humans between the ages of three and four.
Why might crows be promising animals to study? Of course, crows are reputed to
be clever. Aesop's famous fable "The Crow and the Pitcher" tells of a crow
solving a challenging problem: the thirsty crow drops pebbles into a pitcher
with water near the bottom, thereby raising the fluid level high enough to
permit the bird to drink. Such tales are charming and provocative, but science
cannot rely on them.
Recent scientific research sought to
corroborate this fable. It found that crows given a similar problem dropped
stones into a tube containing water, but not into a tube containing sand. Crows
also chose to drop solid rather than hollow objects into the water tube. It thus
seems that crows do indeed understand basic cause-effect relations. Such causal
understanding is no minor feat; children struggle with tasks like this until
they are 5 years old!
Furthermore, crows are renowned for crafting
and using tools. They can carve thin strips of wood into skewers and
bend wires into hooks to collect otherwise inaccessible food.
But, what happens when crows are given problems that require more abstract
thinking? Before setting our sights on analogical reasoning, we might begin with
simpler abstract task. For example, sameness and differentness are key abstract
ideas, because two or more items of any kind--coins, cups, caps, or cars--can be
the same as or different from one another. Because sameness and differentness
can be detected visually, perhaps that may provide an elegant way to study their
apprehension by nonverbal animals.
Animals do readily learn to report sets of identical visual items as "same" and
sets of non-identical items as "different." To do so, we present visual stimuli
on a touchscreen monitor. We reward animals with food for contacting one button
when sets contain identical items and we reward animals for contacting a second
button when sets contain non-identical items. Several species of birds and
mammals learn this task and also transfer their learning to new stimuli, showing
that they have learned an abstract concept, which extends beyond the training
Devising a task to study analogical thinking in animals is the next step. Here,
the gist of analogycan be captured by arranging a matching task in which the
relevant logical arguments are presented in the form of visual stimuli. Using
letters of the alphabet for explanatory purposes, choosing test pair BB would be
correct if the sample pair were AA, whereas choosing test pair EF would be
correct if the sample pair were CD. Stated logically, A:A as B:B (same = same)
and C:D as E:F (different = different). Critically, no items in the correct test
pair physically match any of the items in the sample pair; so, only the
analogical relation of sameness can be used to solve the task.
Early research suggested that only humans and apes can learn this analogy task;
however, a more recent project indicated that baboons
too can learn to select the pair of items that depicts the analogous same or
different relationship as the sample pair.
Now, we have found that crows
too can exhibit analogical thinking. Ed Wasserman, one of the authors of
this article, and his colleagues in Moscow, Anna Smirnova, Zoya Zorina, and
Tanya Obozova, first trained hooded crows on several tasks in which they had to
match items that were the same as one another. The crows were presented with a
tray containing three cups. The middle cup was covered by a card picturing a
color, a shape, or a number of items. The other two side cups were also covered
by cards--one the same as and one different from the middle card. The cup under
the matching card contained food, but the cup under the nonmatching card was
empty. Crows quickly learned to choose the matching card and to do so more
quickly from one task to the next.
Then, the critical test
was given. Each card now pictured a pair of items. The middle card would
display pairs AA or CD, and the two side cards would display pair BB and pair
EF. The relation between one pair of items must be appreciated and then applied
to a new pair of items to generate the correct answer: the BB card in the case
of AA or the EF card in the case of CD. For instance, if the middle card
displayed a circle and a cross, then the correct choice would be the side card
containing a square and a triangle rather than the side card containing two
Not only could the crows correctly perform this task, but they did so
spontaneously, from the very first presentations, without ever being trained to
It seems that initial training to match identical items enabled the crows to
grasp a broadly applicable concept of sameness that could apply to the novel
two-item analogy task. Such robust and uninstructed behavior represents the most
convincing evidence yet of analogical reasoning in a non-primate animal, as only
apes had spontaneously shown analogical reasoning after learning to match
What then are the limits of animal intelligence? That, we assert, is an entirely
empirical question. It is not a question to be answered by anthropocentric
philosophizing. As the author Jack London wrote over a century ago: "You must
not deny your relatives, the other animals. This may be good egotism, but it is
not good science."
ABOUT THE AUTHOR(S)
Leyre Castro, Research Scientist in the Department of Psychology at the
University of Iowa, studies learning and advanced cognition in humans and other
animals. Ed Wasserman, the Stuit Professor of Experimental Psychology in the
Department of Psychology at the University of Iowa, focuses on comparative
analyses of cognition and behavior between humans and other animals.
Are you a scientist who specializes in neuroscience, cognitive science, or
psychology? And have you read a recent peer-reviewed paper that you would like
to write about? Please send suggestions to Mind Matters editor Gareth Cook. Gareth, a Pulitzer
prize-winning journalist, is the series editor of
Best American Infographics and can be
reached at garethideas AT gmail.com or Twitter @garethideas.